1. Field of the Invention
The present invention relates in general to capacitive amplifiers used to identify and trace a particular wire within a group of wires, and more particularly, to a capacitive amplifier having a suppression unit for suppressing unwanted noise signals. The present invention relates also to a tone generator for use in conjunction with the capacitive amplifier.
2. Description of the Relevant Art
Capacitive amplifiers or electric field tone detectors are used by telecommunications, data, alarm or electric service personnel to identify and trace cables in a bundle of cables or inside or behind walls or trace and identify pairs of wires in a bundle of pairs of wires without the need for punctuation, de-insulation or damaging the insulation of the particular wire. These capacitive amplifiers are used in conjunction with low frequency tone generators, also called toners. The toner has to be connected on the known side of the cable or wire pair to inject the tone frequency into the particular wire pair or cable.
The probe tip of the capacitive amplifier has to be moved over the cable or bundle of wire pairs or along a wall to identify the particular connected wire pair conducting the injected audio tone or the cable itself. In this way the cable path or the right pair can be separated from the others. The capacitive amplifier typically includes a built-in loudspeaker which is located opposite the probe tip and which can be used to produce an audible signal derived from the injected audio tone. In addition, terminals may be provided for allowing a rugged service telephone handset, or buttset, to be attached to the capacitive amplifier to reproduce the detected audible tones in the earphone of the buttset.
The normal use of much capacitive amplifiers may, however, be obstructed by noisy environments from power lines or different Linda of electrical devices. Electrical power is provided as an alternating current signal having a frequency of 50 or 60 Hz and for example in areas where power distribution panels for a building are located a power line hum is present which is composed of a 50 or 60 Hz signal plus harmonics thereof. Such noisy signals can be unwantedly picked up by the probe tip and are often much greater than the amplitude of the signal output by the tone generator. Thus finding the location of the desired pair of wires of the desired signal cable is difficult.
Accordingly, it is an object of the present invention to provide a capacitive amplifier adapted to amplify the tone signals provided by a tone generator while suppressing noise signals present in a noisy environment.
It is another object of the present invention to provide a tone generator for use in conjunction with the above capacitive amplifier and for providing tone signals to be detected and amplified by the capacitive amplifier.